92

This study carried out pharyngo-oesophageal cancer (PC) and proventriculus squamous carcinoma induction experiments on chickens, rats and mice by feeding farm compost water to support the etiological hypothesis of nitrogen cycle proposed by Xu (1986a, b). Based on other etiological hypothesis, many works have been done, but up to now, it has not been seen that PC was induced in chickens with high and stable rate by volatile nitrosamines and other carcinogens. Using a rapid composting method, this study prepared compost from 200 kg of corn stalks. 280 chicks were divided into four groups. 100 chicks received feed containing compost water (20% v/w) and NaNO2 (0.04% w/w). Others received feed containing compost water either alone, or NaNO2 alone, or with no addition. Of the 98 chickens remaining in the first group 800 days after the beginning of treatment, subsequently 16 developed PC and 19 had precancerous lesions. No PC was seen in the other three received feed containing compost water alone. The induction rate for PC for the first group was thus 16.3% (16/98), 92 times the natural incidence seen in Linxian county in chickens 5-6 years of age.

A similar experiment was carried out in rats and mice. 270 rats and 300 mice were divided into eight groups. Two experimental groups were fed with large dose (20ml/kg) or low dose (10ml/kg) compost water, respectively. Three interventional groups were treated with three different measures. The remaining was divided into three control groups. 74 weeks after the beginning of treatment, all animals were sacrificed. The incidences of proventriculus squamous carcinoma induced in the rats were 10% of the low dose group and 27.5% of the large dose group. In the mice, the incidences were 8.9% and 26.6%, respectively. No carcinoma was induced in the control groups and interventional group 1.

Subsequently, we used HPLC-PHPS-TEA technique to detect the chemical composition of the compost water. The result demonstrated the presence of N-methy1-N-nitrosourea(MNU) and dimethyl-nitrosamin (NDMA) in the compost water with nitrosation.

The results indicate that precancerous lesion and PC were caused by exposure to compost water, possibly by formation of N-nitroso compounds from their precursors. With a longer experimental period and a higher dose of farm compost water, the incidence of cancer could be expected to be higher. The possible contamination of drinking water by farm compost may therefore be a contributing factor of oesophageal cancer in humans and this possibility needs further study.

References:

Xu, Z. X. Potential Sci., 7 (1), 36-41, 1986a

Xu, Z. X. Potential Sci., 7 (3), 36-40, 1986b

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA